Surface plasmon resonance (SPR) sensing has been demonstrated to be an exceedingly powerful and quantitative probe of the interactions of a variety of chemical and biological processes. SPR sensing provides a means not only for identifying chemical and biological interactions and quantifying their kinetic and energetic properties, but also for employing these interactions as very sensitive chemical and biological detectors. Conventional SPR sensing is performed using plasmons generated at a metal/dielectric interface, with the metal commonly being gold. See, for example, J. Homola et al., “Surface Plasmon Resonance Sensors: Review,” Sensors and Actuators B: Chemical 54, 3 (January 1999).
Conventional metal-based plasmonic materials, however, have certain notable limitations. They are designed to operate at predetermined resonance frequencies, which cannot be substantially tuned. Furthermore, the use of metals requires three dimensional design of plasmon-generating structures, and the plasmon field confinement and propagation length are determined by the metal conductivity. It is in these ways that conventional metal-based plasmonic materials are limited.
Thus, improved plasmonic materials for SPR sensing would be desirable.